White male voters are increasingly turning away from the Democratic party, according to a recent Gallup poll, and the shift could prove decisive in November's midterm elections. Here, a brief primer on why white men are making the move, and how the change affects the electoral math:

How many white male voters are leaving the Dems?According to a recent Gallup poll, only 35 percent of white males said they would back the Democrats in the fall election. That figure has dropped 8 percentage points since July 2009. White male support for President Obama has dropped, too -- from 41 percent in the election of 2008 to 38 percent now.

Why are they leaving?One explanation: The "he-cession," says David Paul Kuhn in the Los Angeles Times. "Nearly half" of those who lost their jobs in the recession are white males. Between "financial bailouts for the rich folks" and a "healthcare bailout for the poor folks," the ordinary white male voter feels "forgotten" and angry.

Is that the only reason?That theory is popular among conservative commentators, but some of their liberal counterparts chalk up the change to race-baiting by Republicans. With "catcalls, joker posters, N word slurs," and boisterous tea parties, says Earl Ofari Hutchinson in The Daily Voice, conservatives have rekindled the notion that Democrats want to raise taxes to create social programs for minorities "at the expense of hard-working whites." It's the same "win with white vote strategy" the GOP has used for a half century.

How might the shift affect the fall vote?Obama won big in 2008 partly because he attracted the highest percentage of white male voters for a Democrat in 30 years. "Unless the president and his party find a way to reverse" the white exodus and address the anger of the millions of white men who have lost faith in them, says Wesley Pruden in The Washington Times, "they must prepare for an epic bath" in the November midterm elections.

Will these numbers really tip the balance?Many factors will come into play. One of the most important, says Tom Schaller in FiveThirtyEight, is whether the "Obama surge voters" go to the polls. Millions of first-time voters came out to support Obama in 2008. The numbers put Obama over the top in states that had leaned Republican for years. But it's anybody's guess whether those voters will return in the fall without Obama on the ballot. If they show up, they could buffer "expected Democratic losses." If not, Obama's party could be in for deep pain.